‘I’m itching for a fight on a whole range of issues.” President Barack Obama made that threat last week as Congress moved to pass his bipartisan tax-cut compromise. Why was Mr. Obama so pugilistic?

It was partly to reassure unhappy Democratic liberals, especially bitter Democratic congressmen. Many are from gerrymandered districts where little news about the midterm elections has apparently penetrated.

But a scorched-earth policy doesn’t make sense for the Obama White House. Independents voted Republican last month by a 59% to 38% margin not because they thought Mr. Obama too civil, his course too centrist, and his bipartisanship too energetic. In fact, they were sick of the administration’s direction and tone. The increased number of Republicans in Congress next year will stop Mr. Obama’s leftward policy march, whether he likes it or not. But only he can change his manner of speaking.

In his first two White House years, Mr. Obama has seemed incapable of constructing a positive narrative. Instead, he has appeared hard-wired to justify his policy choices by blaming savage evildoers for monstrous wrongs.

Mr. Obama fell into this habit early. He kicked off his drive to pass a stimulus on Jan. 8, 2009 by attacking the “profound irresponsibility that stretched from corporate boardrooms to . . . Washington.” In December of that year, during a “60 Minutes” interview, he lashed out at bankers making multimillion-dollar bonuses, saying “I did not run for office to be helping out a bunch of fat-cat bankers on Wall Street.”